This invention relates in general to cutting instruments and, more particularly, to a surgical knife which is particularly adapted for use in removing the semilunar cartilages from the knee.
The surgical removal of damaged semilunar cartilage from the human knee cavity, which desirably is done through a small incision anterior to the knee joint, presents several specific surgical difficulties. The incision is deepened through the skin and the subcutaneous tissue directly through the capsular structure of the knee. The anterior portion of the meniscus is quite easily detached from the tibia and the surrounding soft tissues, but as the cutting proceeds rearwardly to the posterior corner of the knee removal of this tissue becomes quite difficult. At this point the meniscus is held basically by two sets of strong collagenous fibers, namely, those running from the surface of the tibia onto the cartilagenous meniscus, and those running at a right angle to it, as extensions of the capsule of the knee joint.
One type of surgical knife currently used in the removal of semilunar cartilage from the knee consists of an elongated flat blade have a handle-engaging shank at one end, is curved slightly toward its forward end, and has a cutting edge at its front end. This type of knife is manufactured and sold by Rudolph Beaver, Inc., Belmont, Massachusetts. Another knife of the same general type is described in U.S. Pat. No. 3,221,744, consisting of an elongated body member the rear end of which serves as a handle. The body member has a curved cutting head near the front end thereof, and a removable and replaceable cutting blade is firmly supported upon the cutting head so that its cutting edge extends toward the front end of the instrument. When either of these two types of knife is used in knee surgery, the cutting edge is swept back in one of the aforementioned planes to cut the corresponding attachment, and then, after withdrawing the handle, the blade is turned through an angle of 90.degree. so as to be positioned to cut those fibers constituting the other attachment. In either plane, the cutting edge is not visible to the surgeon, particularly from the posterior corner and beyond, and as a consequence the cutting edge is sometimes forced into and damages either the supporting structure at the posterior medial or the posterior lateral corners of the knee joint capsule, leading to latent instability. Should a surgical instrument of this type be pushed back against the knee joint, into the poplitial space where the major neural vascular structures of the lower extremity run through it, serious damage can result.
Another type of surgical instrument heretofore used for removing the cartilage from the knee has curved tracks which are inserted into the knee capsule for guiding a cutting blade slidable thereon. A form of this type of instrument is disclosed in U.S. Pat. No. 3,835,859 and includes a flexible track operatively connected to a handle and adapted to be extended therefrom into the knee cavity to conform to the interior configuration of the knee cavity, and a blade slidably mounted on the track and constrained to move thereon for cutting damaged or broken cartilage. Instruments of this type are cumbersome to use, and because of the restricted visibility at and beyond the posterior corner of the meniscus, a high degree of mechanical dexterity is required to ensure that insertion of the flexible wires constituting the track does not damage the supporting structure of the knee. Such instruments are also relatively expensive, adding to the already relatively high cost of performing this type of knee operation.
It is the object of the present invention to provide an improved surgical knife which is particularly adaptable for use in removing the semilunar cartilages from the knee which is simple in construction, relatively inexpensive to manufacture, amenable to sterilized packaging and which is disposable following use for a single procedure.